Method of forming fin-shaped structure

ABSTRACT

A fin-shaped structure includes a substrate having a first fin-shaped structure located in a first area and a second fin-shaped structure located in a second area, wherein the second fin-shaped structure includes a ladder-shaped cross-sectional profile part. The present invention also provides two methods of forming this fin-shaped structure. In one case, a substrate having a first fin-shaped structure and a second fin-shaped structure is provided. A treatment process is performed to modify an external surface of the top of the second fin-shaped structure, thereby forming a modified part. A removing process is performed to remove the modified part through a high removing selectivity to the first fin-shaped structure and the second fin-shaped structure, and the modified part, thereby the second fin-shaped structure having a ladder-shaped cross-sectional profile part is formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and claims the benefitof U.S. patent application Ser. No. 15/688,885, which is a divisionalapplication of and claims the benefit of U.S. patent application Ser.No. 14/512,475, filed Oct. 13, 2014.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a fin-shaped structure andmethod thereof, and more specifically to a fin-shaped structure whichhas a ladder-shaped cross-sectional profile, and a method thereof.

2. Description of the Prior Art

With increasing miniaturization of semiconductor devices, variousmulti-gate MOSFET devices have been developed. The multi-gate MOSFET isadvantageous for the following reasons. Manufacturing processes ofmulti-gate MOSFET devices can be integrated into traditional logicdevice processes, and thus are more compatible. In addition, since thethree-dimensional structure of the multi-gate MOSFET increases theoverlapping area between the gate and the substrate, the channel regionis controlled more effectively, which reduces drain-induced barrierlowering (DIBL) effect and short channel effect. Moreover, the channelregion is longer for the same gate length, so the current between thesource and the drain is increased.

Since transistors in different areas such as logic areas andinput/output areas have different purposes, structures of thesetransistors should be tailored to suit their particular purposes. Whenforming the structures, electrical demands in each area should beconsidered.

SUMMARY OF THE INVENTION

The present invention provides a fin-shaped structure and methodthereof, which selectively forms fin-shaped structures havingladder-shaped cross-sectional profile parts in some areas, so thatfin-shaped structures of different heights and critical dimensions (CD)can be formed, in order to form transistors for each area that meet eacharea's specific electrical demands.

The present invention provides a fin-shaped structure including asubstrate having a first fin-shaped structure located in a first areaand a second fin-shaped structure located in a second area, wherein thesecond fin-shaped structure includes a ladder-shaped cross-sectionalprofile part.

The present invention provides a method of forming a fin-shapedstructure including the following steps. A substrate having a firstfin-shaped structure located in a first area and a second fin-shapedstructure located in a second area is provided. An isolation structureis filled beside the first fin-shaped structure of the first area andbeside the second fin-shaped structure of the second area. A patternedmask is formed to cover the first area and expose the second area. A toppart of the isolation structure of the second area is removed, to exposea first top part of the second fin-shaped structure. A treatment processis performed to modify an external surface of the first top part of thesecond fin-shaped structure, to form a modified part covering the firsttop part of the second fin-shaped structure. The patterned mask isremoved. A removing process is performed to remove a part of theisolation structure and the modified part by the high removingselectivity to the first fin-shaped structure and the second fin-shapedstructure, and the modified part and the isolation structure, to exposea top part of the first fin-shaped structure and a second top part ofthe second fin-shaped structure.

The present invention provides a method of forming a fin-shapedstructure including the following steps. A substrate having a firstfin-shaped structure located in a first area and a second fin-shapedstructure located in a second area is provided. A first gate across thefirst fin-shaped structure and a second gate across the secondfin-shaped structure are formed, wherein the first gate sequentiallyincludes a first dielectric layer and a first sacrificial gate coveringthe first fin-shaped structure, and the second gate sequentiallyincludes a second dielectric layer and a second sacrificial gatecovering the second fin-shaped structure. The first sacrificial gate andthe second sacrificial gate are removed, thereby exposing the firstdielectric layer and the second dielectric layer. A mask covers thefirst area and exposes the second area. A removing process is performedto remove an external surface of a top part of the second fin-shapedstructure. The mask is then removed.

According to the above, the present invention provides a fin-shapedstructure and method thereof, which covers a mask in a first area, andthen removes an external surface of a top part of a second fin-shapedstructure of a second area, so that the second fin-shaped structurehaving a ladder-shaped cross-sectional profile in the second area isformed. Hence, fin-shaped structures of different heights and criticaldimensions can be formed, and thus transistors for each area can achieverequired electrical requirements. The methods of removing the externalsurface of the top part of the second fin-shaped structure in the secondarea may include: a removing process is performed to directly remove theexternal surface of the top part of the second fin-shaped structure; or,a treatment process may be performed to modify the external surface ofthe top part of the second fin-shaped structure, and a removing processmay be performed to remove the modified part.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 schematically depict a cross-sectional view of a method offorming a fin-shaped structure according to a first embodiment of thepresent invention.

FIGS. 6-10 schematically depict a cross-sectional view of a method offorming a fin-shaped structure according to a second embodiment of thepresent invention.

DETAILED DESCRIPTION

FIGS. 1-5 schematically depict a cross-sectional view of a method offorming a fin-shaped structure according to a first embodiment of thepresent invention. As shown in FIG. 1, a substrate 110 is provided. Thesubstrate 110 can be divided into a first area A and a second area B. Inthis embodiment, the first area A is a high voltage threshold (HVT) areawhile the second area B is a low voltage threshold (LVT) area, but thisis not limited thereto. The first area A may be an input/output highvoltage area while the second area B may be a logic area. Forillustrating the present invention clearly, there are only two areasdepicted in this embodiment, but the present invention can also beapplied to three or more areas at the same time, depending uponpractical requirements.

The substrate 110 has two first fin-shaped structures 112 a in the firstarea A and two second fin-shaped structures 112 b in the second area B.In this embodiment, two first fin-shaped structures 112 a are formed inthe first area A and two second fin-shaped structures 112 b are formedin the second area B, but the number of the first fin-shaped structures112 a or the second fin-shaped structures 112 b is not restrictedthereto. In this embodiment, the first fin-shaped structures 112 a andthe second fin-shaped structures 112 b have the same structure. A heighth1 of each of the first fin-shaped structures 112 a is common to aheight h2 of each of the second fin-shaped structures 112 b; a width w1of a top part of each of the first fin-shaped structures 112 a is thesame as a width w2 of a top part of each of second fin-shaped structures112 b; and a first distance p1 between a top part of each of the firstfin-shaped structures 112 a is the same as a distance p2 between a toppart of each of the second fin-shaped structures 112 b. Therefore, whena selective treatment process is performed on one single area or on aplurality of areas, symmetric structures in these areas will receive thesame influence and uniform structures can be formed. The first distancep1 between a top part of each of the first fin-shaped structures 112 amay also be different from the distance p2 between a top part of each ofthe second fin-shaped structures 112 b.

More precisely, the method of forming the first fin-shaped structures112 a in the first area A and forming the second fin-shaped structures112 b in the second area B may include, but is not limited to, thefollowing steps. A bulk bottom substrate (not shown) is provided. A hardmask layer (not shown) may be formed on the bulk bottom substrate (notshown) and is patterned to define the location of the first fin-shapedstructures 112 a and the second fin-shaped structures 112 b in the bulkbottom substrate (not shown) by a sidewall image transfer process. Anetching process is performed to form the first fin-shaped structures 112a and the second fin-shaped structures 112 b. The first fin-shapedstructures 112 a and the second fin-shaped structures 112 b located inthe substrate 110 are then formed completely. In one embodiment, thehard mask layer (not shown) is removed after the first fin-shapedstructures 112 a and the second fin-shaped structures 112 b are formed,and a tri-gate MOSFET can be formed in the following processes. Thereare three contact faces between the first fin-shaped structures 112 aand the second fin-shaped structures 112 b and the following formeddielectric layer functions as a carrier channel whose width is widerthan a channel width in a conventional planar MOSFET. When a drivingvoltage is applied, the tri-gate MOSFET produces a double on-currentcompared to the conventional planar MOSFET. In another embodiment, thehard mask layer (not shown) is reserved to form a fin field effecttransistor (Fin FET), which is another kind of multi-gate MOSFET. Due tothe hard mask layer (not shown) being reserved in the fin field effecttransistor, there are only two contact faces between the firstfin-shaped structures 112 a and the second fin-shaped structures 112 band the following formed dielectric layer.

The present invention can also be applied to other semiconductorsubstrates. For example, a silicon-on-insulator substrate (not shown) isprovided, and then a single crystalline silicon layer being a top partof the silicon-on-insulator substrate (not shown) is etched till anoxide layer being a middle part of the silicon-on-insulator substrate(not shown) is exposed.

Isolation structures 10 a and 10 b are filled beside the firstfin-shaped structures 112 a in the first area A and beside the secondfin-shaped structures 112 b in the second area B. The isolationstructures 10 a and 10 b may be shallow trench isolation (STI)structures, and may include oxide, but are not limited thereto. In thisembodiment, the isolation structures 10 a and 10 b are filled beside thefirst fin-shaped structures 112 a in the first area A and beside thesecond fin-shaped structures 112 b in the second area B simultaneously,and the isolation structures 10 a and 10 b have the same height.Therefore, symmetric structures are formed in the first area A and thesecond area B. As a selective treatment process is performed on onesingle area or on a plurality of areas, symmetric structures in theseareas can receive the same influence and thus uniform structures can beformed. In another embodiment, the isolation structures 10 a and 10 bmay have different heights and may be formed by different processes,depending upon practical requirements.

After the first fin-shaped structures 112 a and the second fin-shapedstructures 112 b are formed, a doping process may be selectivelyperformed to form wells in the first area A and the second area B or tochange threshold voltages in the two areas.

A patterned mask 20 a is then formed to cover the first area A butexpose the second area B. As shown in FIG. 1, a mask 20 blanket-coversthe first area A and the second area B. A photoresist (not shown) isdeposited and patterned to form a patterned photoresist K1 on the mask20, wherein the patterned photoresist K1 covers the first area A butexposes the second area B. Thereafter, an etching process is performedto remove the exposed mask 20 in the second area B, so a patterned mask20 a is formed only in the first area A. Then, the patterned photoresistK1 is removed, as shown in FIG. 2. In this embodiment, the patternedmask 20 a is a silicon nitride layer, but it is not limited thereto.

A removing process Q1 may be performed to remove a top part 10 bt of theisolation structure 10 b in the second area B, to form an isolationstructure 10 b 1 and expose first top parts 112 b 1 of the secondfin-shaped structures 112 b, as shown in FIG. 3. It is emphasized that,due to the patterned mask 20 a blanket-covering the first area A, theisolation structure 10 a and the first fin-shaped structures 112 a arereserved completely without being removed. In this embodiment, theremoving process Q1 may be an ammonia and nitrogen trifluoridecontaining etching process, which has a high etching selectivity to theisolation structure 10 b and the second fin-shaped structures 112 b;that is, the etching rate of the removing process Q1 to the isolationstructure 10 b is much larger than to the second fin-shaped structures112 b, so only the isolation structure 10 b is removed without removingthe second fin-shaped structures 112 b. In another embodiment, theremoving process Q1 may be other processes, but these processes musthave high removing selectivity to the isolation structure 10 b and thesecond fin-shaped structures 112 b in order to remove a part of theisolation structure 10 b and expose a part of the second fin-shapedstructures 112 b.

As shown in FIG. 4, a treatment process Q2 is performed to modify anexternal surface T1 of a first top part 112 b 1 of each of the secondfin-shaped structures 112 b, thereby a modified part 120 covering thefirst top part 112 b 1 of each of the second fin-shaped structures 112 bis formed. In this embodiment, due to the isolation structures 10 a and10 b being composed of oxide, the modified parts 120 are preferablycomposed of oxide, for being removed together with the isolationstructures 10 a and 10 b in later processes. The treatment process Q2 ispreferably an oxidation process, which may be an oxygen gas-containingprocess or an in situ steam generation (ISSG) process.

After the modified parts 120 are formed, the patterned mask 20 a isremoved, as shown in FIG. 5. Thereafter, a removing process Q3 isperformed to remove the modified parts 120 and a part of the isolationstructures 10 a and 10 b 1 simultaneously, to form a top part 112 a 1 ofeach of the first fin-shaped structures 112 a and a second top part 112b 2 of each of the second fin-shaped structures 112 b. In thisembodiment, the modified parts 120 and the part of the isolationstructures 10 a and 10 b 1 are removed simultaneously without removingthe first fin-shaped structures 112 a and the second fin-shapedstructures 112 b by the high removing selectivity of the removingprocess Q3 to the first fin-shaped structures 112 a and the secondfin-shaped structures 112 b, and the modified part 120 and the isolationstructures 10 a and 10 b 1.

Each of the second fin-shaped structures 112 b having a ladder-shapedcross-sectional profile part C1 can be formed while reserving theoriginal first fin-shaped structures 112 a. The ladder-shapedcross-sectional profile part C1 has a bending angle θ1, which ispreferably larger than or equal to 90°. It is emphasized that a specificfollowing structure is formed by applying the method of forming afin-shaped structure of the present invention. The width w1 of the toppart of each of the first fin-shaped structures 112 a comprising a firstfin and a second fin is larger than a width w3 of a top part of each ofthe second fin-shaped structures 112 b comprising a third fin and afourth fin. The first distance p1 between adjacent top corners of thefirst fin and the second fin of the first fin-shaped structures 112 a isless than a second distance p3 between adjacent top corners of the thirdfin and the fourth fin of the second fin-shaped structures 112 b while athird distance p5 between adjacent lower parts of the first fin and thesecond fin is the same as a fourth distance p6 between adjacent lowerparts of the third fin and the fourth fin. The ladder-shapedcross-sectional profile part C1 of each of the second fin-shapedstructures 112 b is higher than a top surface T2 of the isolationstructure 10 b 1. A top surface T3 of the isolation structure 10 a inthe first area A is higher than the top surface T2 of the isolationstructure 10 b 1 in the second area B. A height h3 of each of the firstfin-shaped structures 112 a protruding from the isolation structure 10 ais lower than a height h4 of each of the second fin-shaped structures112 b protruding from the isolation structure 10 b 1. The height h1 ofeach of the first fin-shaped structures 112 a protruding from thesubstrate 110 is higher than a height h5 of each of the secondfin-shaped structures 112 b protruding from the substrate 110.

Thereafter, processes such as forming gates or transistors may beperformed. For instance, a gate may be formed across the firstfin-shaped structures 112 a of the first area A and the secondfin-shaped structures 112 b of the second area B respectively; asource/drain may be formed in the first fin-shaped structures 112 a andthe second fin-shaped structures 112 b beside the gates respectively;and an interdielectric layer may be formed to cover the gates, the firstfin-shaped structures 112 a and the second fin-shaped structures 112 b.

The first fin-shaped structures 112 a and the second fin-shapedstructures 112 b having ladder-shaped cross-sectional profile parts C1are formed and then the gates are formed on the first fin-shapedstructures 112 a and the second fin-shaped structures 112 b, thereby thewhole second fin-shaped structures 112 b of the second area B have aladder-shaped cross-sectional profile parts C1 in the first embodiment.

A second embodiment is presented in the following. Common firstfin-shaped structures and second fin-shaped structures are formedfirstly and gates are formed across the first fin-shaped structures andthe second fin-shaped structures, and then parts of the first fin-shapedstructures and the second fin-shaped structures are exposed to form thesecond fin-shaped structures having ladder-shaped cross-sectionalprofile parts by applying the present invention. In this way, only theparts of the second fin-shaped structure right below the gates have theladder-shaped cross-sectional profile parts.

FIGS. 6-10 schematically depict a cross-sectional view of a method offorming a fin-shaped structure according to a second embodiment of thepresent invention. As shown in FIG. 6, a substrate 110 is provided. Thesubstrate 110 can be divided into a first area A and a second area B. Inthis embodiment, two first fin-shaped structures 212 a are formed in thefirst area A and two second fin-shaped structures 212 b are formed inthe second area B, but the number of the first fin-shaped structures 212a or the second fin-shaped structures 212 b is not restricted thereto.As in the first embodiment, the first fin-shaped structures 212 a andthe second fin-shaped structures 212 b are common structures. Therefore,symmetric structures are formed in the first area A and the second areaB. When a selective treatment process performed on one single area or ona plurality of areas, symmetric structures in these areas can receivethe same influence and thus uniform structures can be formed. Themethods of forming the first fin-shaped structures 212 a and the secondfin-shaped structures 212 b which are common to those of the firstembodiment are not described herein.

Isolation structures 30 a and 30 b are filled beside the firstfin-shaped structures 212 a in the first area A and beside the secondfin-shaped structures 212 b in the second area B respectively. Theisolation structures 30 a and 30 b may be shallow trench isolation (STI)structures, and may include oxide. In this embodiment, the isolationstructures 10 a and 10 b are filled beside the first fin-shapedstructures 212 a in the first area A and beside the second fin-shapedstructures 212 b in the second area B simultaneously, therefore theisolation structures 30 a and 30 b will have the same height. Symmetricstructures are formed in the first area A and the second area B. When aselective treatment process is performed on one single area or on aplurality of areas, symmetric structures in these areas can receive thesame influence and thus uniform structures can be formed. In anotherembodiment, the isolation structures 30 a and 30 b may have differentheights and maybe formed by different processes, depending uponpractical requirements. Moreover, after the first fin-shaped structures212 a and the second fin-shaped structures 212 b are formed, a dopingprocess may be selectively performed to form wells in the first area Aand the second area B respectively or to change threshold voltages inthe two areas.

A first gate 220 a is formed across the first fin-shaped structures 212a of the first area A and a second gate 220 b is formed across thesecond fin-shaped structures 212 b of the second area B. More precisely,the first gate 220 a may include a first dielectric layer 222 a and afirst sacrificial gate 224 a from bottom to top to cover the firstfin-shaped structures 212 a, and the second gate 220 b may include asecond dielectric layer 222 b and a second sacrificial gate 224 b frombottom to top to cover the second fin-shaped structures 220 b. Spacers230 a and 230 b may be formed on the isolation structures 30 a and 30 bbeside the first gate 220 a and the second gate 220 b respectively.Interdielectric layers 240 a and 240 b may be formed to blanket thesubstrate 110 beside the first gate 220 a and the second gate 220 b. Inthis embodiment, the first dielectric layer 222 a and the seconddielectric layer 222 b may be oxide layers, the first sacrificial gate224 a and the second sacrificial gate 224 b may be polysilicon gates,the spacers 230 a and 230 b maybe nitride spacers, and theinterdielectric layers 240 a and 240 b may be oxide layers, but this isnot limited thereto. The methods of forming the first gate 220 a and thesecond gate 220 b, the spacers 230 a and 230 b and the interdielectriclayers 240 a and 240 b are known in the art, and are not describedherein.

An etching process may be performed to remove the first sacrificial gate224 a and the second sacrificial gate 224 b and expose the firstdielectric layer 222 a and the second dielectric layer 222 b, to therebyform recesses R1 and R2 in the first area A and the second area Brespectively, as shown in FIG. 7.

As shown in FIG. 8, a mask K2 is formed to cover only the first area Abut expose the second area B. In this embodiment, the mask K2 fills therecess R1 of the first area A. FIGS. 7-8 illustrate a removing processQ4 being performed to remove an external surface S1 of a top part ofeach of the second fin-shaped structures 212 b (as shown in FIG. 7), toform second fin-shaped structures 212 b′ having ladder-shapedcross-sectional profile parts C2, wherein the ladder-shapedcross-sectional profile parts C2 have a bending angle θ2, and thebending angle θ2 is preferably larger than or equal to 90°. In thisembodiment, the second dielectric layer 222 b and the top part 30 bt ofthe isolation structure 30 b below the second dielectric layers 222 bare removed as the removing process Q4 is performed to remove theexternal surfaces S1 of the second fin-shaped structures 212 b. Anisolation structure 30 b 1 is formed, and a top surface T4 of theisolation structure 30 b 1 at the bottom of the recess R2 is lower thana top surface T5 of isolation structure 30 b 1 beside the recess R2, andeven lower than a top surface T6 of the isolation structure 30 a in thefirst area A, depending upon the etchants of the removing process Q4 anda desired formed structure. In another embodiment, modified parts may beformed from the top parts of the second fin-shaped structures 212 b asdescribed in the first embodiment, and then the modified parts areremoved.

It is emphasized that, since the second dielectric layer 222 b and thesecond fin-shaped structures 212 b below the second dielectric layer 222b are removed by the removing process Q4, the removing process Q4 hasnon-removing selectivity to the second dielectric layer 222 b and thesecond fin-shaped structures 212 b. This means the removing rate of theremoving process Q4 to the second dielectric layer 222 b is equal tothat of the second fin-shaped structures 212 b. In one case, theremoving process Q4 may be a fluorine containing process. Since thesecond dielectric layer 222 b is an oxide layer and the isolationstructure 30 b is composed of oxide, a part of the isolation structure30 b in the recess R2 is also removed when the removing process Q4 forremoving the second dielectric layer 222 b is performed.

After the second fin-shaped structures 212 b′ having ladder-shapedcross-sectional profile parts C2 are formed, the mask K2 and the firstdielectric layer 222 a in the first area A are removed, as shown in FIG.9. In this embodiment, the mask K2 may be removed by an θ2 strippingprocess, and the first dielectric layer 222 a may be removed by anammonia and nitrogen trifluoride containing etching process, but this isnot limited thereto. As shown in FIG. 10, dielectric layers 250 a and250 b cover the first fin-shaped structures 212 a and the secondfin-shaped structures 212 b′ respectively. The dielectric layers 250 aand 250 b may be formed by the same process and have the same thickness,or may be formed by different processes or materials to have differentthicknesses. For instance, the first area A is a high voltage threshold(HVT) area while the second area B is a low voltage threshold (LVT)area, so the thickness of the dielectric layer 250 a of the first area Ais larger than the thickness of the dielectric layer 250 b of the secondarea B; or, the materials of the dielectric layers 250 a and 250 b maybe different, enabling the dielectric layer 250 a to have the capabilityof preventing high voltages while the dielectric layer 250 b has lowerEquivalent Oxide Thickness (EOT).

In this embodiment, the first dielectric layer 222 a is removed and thenthe dielectric layers 250 a and 250 b are reformed. In otherembodiments, the first dielectric layer 222 a may not be removed whilethe dielectric layers 250 a and 250 b are formed directly on the firstdielectric layer 222 a; or, only the dielectric layer 250 b in thesecond area B is formed. As shown in FIGS. 8-9, the mask K2 is formed,and the first dielectric layer 222 a is then removed completely in thisembodiment. In another embodiment, the first dielectric layer 222 a andthe second dielectric layer 222 b may be removed before the mask K2 isformed.

To summarize, the present invention provides a fin-shaped structure andmethod thereof, which covers a mask in a first area, and then removes anexternal surface of a top part of a second fin-shaped structure of asecond area, so that a part, or all, of the second fin-shaped structuresin the second area having ladder-shaped cross-sectional profiles can beformed. Hence, fin-shaped structures having different heights andcritical dimensions can be formed in different areas, and thustransistors for each area can achieve their electrical requirements.

The methods of removing the external surface of the top part of thesecond fin-shaped structure in the second area after covering the maskin the first area may include: performing a removing process to directlyremove the external surface of the top part of the second fin-shapedstructure, wherein the removing process has non-removing selectivity tothe second fin-shaped structure and materials except for those above thesecond fin-shaped structure such as dielectric layers or isolationstructures, to remove them. In addition, a treatment process may beperformed to modify the external surface of the top part of the secondfin-shaped structure in the second area, and then the removing processis performed to remove the modified part, wherein the removing processhas high removing selectivity to the modified part and the originalsecond fin-shaped structure, so that the modified part can be removedwithout removing the second fin-shaped structure.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of forming a fin-shaped structure,comprising: providing a substrate having a first fin-shaped structurelocated in a first area and a second fin-shaped structure located in asecond area; forming a first gate across the first fin-shaped structureand a second gate across the second fin-shaped structure, wherein thefirst gate sequentially comprises a first dielectric layer and a firstsacrificial gate covering the first fin-shaped structure, and the secondgate sequentially comprises a second dielectric layer and a secondsacrificial gate covering the second fin-shaped structure; removing thefirst sacrificial gate and the second sacrificial gate, thereby exposingthe first dielectric layer and the second dielectric layer; covering amask in the first area but exposing the second area; performing aremoving process to remove an external surface of a top part of thesecond fin-shaped structure; and removing the mask.
 2. The method offorming a fin-shaped structure according to claim 1, further comprising:forming a dielectric layer covering the first fin-shaped structure andthe second fin-shaped structure after the mask is removed.
 3. The methodof forming a fin-shaped structure according to claim 1, wherein theexternal surface of the top part of the second fin-shaped structure andthe whole second dielectric layer are removed by the removing process.4. The method of forming a fin-shaped structure according to claim 1,further comprising: removing the first dielectric layer completely afterthe mask is removed.
 5. The method of forming a fin-shaped structureaccording to claim 1, further comprising: removing the first dielectriclayer and the second dielectric layer completely before covering themask.
 6. The method of forming a fin-shaped structure according to claim1, further comprising: forming an isolation structure beside the firstfin-shaped structure of the first area and beside the second fin-shapedstructure of the second area respectively after the substrate isprovided, wherein a top part of the isolation structure of the secondarea is also removed while the removing process is performed.
 7. Themethod of forming a fin-shaped structure according to claim 1, whereinthe removing process has no removing selectivity to the isolationstructure and the second fin-shaped structure.